Scoliosis imaging: An analysis of radiation risk in the CT scan projection radiograph and a comparison with projection radiography and EOS

Scoliosis

Scoliosis is a three-dimensional spinal deformity that can occur at any age. It may be idiopathic or secondary in children, idiopathic and degenerative in adults. Management of patients with scoliosis is multidisciplinary, involving rheumatologists, radiologists, orthopaedic surgeons, and prosthetists. Imaging plays a central role in diagnosis, including the search for secondary causes, follow-up, and preoperative work-up if surgery is required. Evaluating scoliosis involves obtaining frontal and lateral full-spine radiographs in the standing position, with analysis of coronal and sagittal alignment. For adolescent idiopathic scoliosis, imaging follow-up is often required, accomplished using low-dose stereoradiography such as EOS imaging. For adult degenerative scoliosis, the crucial characteristic is rotatory subluxation, also well detected on radiographs. Magnetic resonance imaging is usually more informative than computed tomography for visualizing associated canal and foraminal stenoses. Radiologists must also have a thorough understanding of postoperative features and complications of scoliosis surgery because aspects can be misleading.

Development and Validation of a Mobile Application for Measuring Tibial Torsion

BACKGROUND

Tibial torsion lacks a single and reliable method for its measurement. While physical examination, computed tomography (CT), and EOS imaging are used complementarily, three-dimensional (3D) CT is the most widely used method for intuitive documentation and visualization. However, concern regarding the associated radiation hazard limits its use in the evaluation of pediatric patients. Moreover, EOS machines are too expensive and too large to be placed in every clinic requiring the measurement of tibial torsion. Therefore, a new method for 3D reconstruction is needed. In the present study, we tested the validity and reliability of a novel reconstruction tool for the lower leg.

METHODS

A statistical shape model and Laplacian constraint were adopted for the development of a new reconstruction tool for measuring tibial torsion. Tibial torsion measurements based on a 3D reconstruction application and CT images for 36 patients were evaluated for intraobserver and interobserver reliability. Tibial torsion measurements for 75 patients were compared for validation.

RESULTS

A 3D reconstruction system for the lower leg was developed as a mobile application and was installed in a portable device for easy access in the clinical setting. In terms of interobserver reliability, the intraclass correlation coefficient among 3 clinicians was 0.896 (95% confidence interval [CI], 0.828 to 0.941). The correlation coefficient between tibial torsion measured with use of 3D CT and that measured with the mobile application was 0.865 (p < 0.001).

CONCLUSIONS

The mobile application showed excellent reliability and validity for measuring tibial torsion. Concurrent utilization with mobile application for the femur allows visualization of the rotational profile of the leg without the need for CT or EOS.

LEVEL OF EVIDENCE

Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Ultrasound to X-ray synthesis generative attentional network (UXGAN) for adolescent idiopathic scoliosis

Standing X-ray radiograph with Cobb's method is the gold standard for scoliosis diagnosis. However, radiation hazard restricts its application, especially for close follow-up of adolescent patients. Compared with X-ray, ultrasound imaging has advantages of being radiation-free and real-time. To combine advantages of the above two imaging modalities, an ultrasound to X-ray synthesis generative attentional network (UXGAN) was proposed to synthesize ultrasound images into X-ray-like images. In this network, a cyclically consistent network was adopted and was trained end-to-end. An attention module was added and different residual blocks were designed. The quantitative comparison results demonstrated the superiority of our method to the state-of-the-art CycleGAN methods. We further compared the Cobb angle values measured on synthesized images and the real X-ray images, respectively. A good linear correlation (r = 0.95) was demonstrated between the two methods. The above results proved that the proposed method is of great significance for providing both X-ray images and ultrasound images based on the radiation-free ultrasound scanning.

Feature Importance Analysis for Postural Deformity Detection System Using Explainable Predictive Modeling Technique

This study aimed to analyze feature importance by applying explainable artificial intelligence (XAI) to postural deformity parameters extracted from a computer vision-based posture analysis system (CVPAS). Overall, 140 participants were screened for CVPAS and enrolled. The main data analyzed were shoulder height difference (SHD), wrist height difference (WHD), and pelvic height difference (PHD) extracted using a CVPAS. Standing X-ray imaging and radiographic assessments were performed. Predictive modeling was implemented with XGBoost, random forest regressor, and logistic regression using XAI techniques for global and local feature analyses. Correlation analysis was performed between radiographic assessment and AI evaluation for PHD, SHD, and Cobb angle. Main global features affecting scoliosis were analyzed in the order of importance for PHD (0.18) and ankle height difference (0.06) in predictive modeling. Outstanding local features were PHD, WHD, and KHD that predominantly contributed to the increase in the probability of scoliosis, and the prediction probability of scoliosis was 94%. When the PHD was >3 mm, the probability of scoliosis increased sharply to 85.3%. The paired t-test result for AI and radiographic assessments showed that the SHD, Cobb angle, and scoliosis probability were significant (p < 0.05). Feature importance analysis using XAI to postural deformity parameters extracted from a CVPAS is a useful clinical decision support system for the early detection of posture deformities. PHD was a major parameter for both global and local analyses, and 3 mm was a threshold for significantly increasing the probability of local interpretation of each participant and the prediction of postural deformation, which leads to the prediction of participant-specific scoliosis.

Comparison of slot-scanning standing, supine, and fulcrum radiographs for assessment of curve flexibility in adolescent idiopathic scoliosis: a pilot study

PURPOSE

With the goal of reducing radiation dosing for patients, we sought to compare the results of slot-scanning (EOS) standing flexibility radiographs to supine bending and fulcrum radiographs for surgical planning in adolescent idiopathic scoliosis (AIS). We hypothesized that slot-scanning standing bending radiographs provide similar mean curve flexibility as supine bending and fulcrum radiographs.

METHODS

This is a retrospective review of 224 AIS patients with concomitant upright standing and flexibility images. Curve flexibility, defined the percent change in Cobb angle from standing upright to flexibility images, was used to compare the results of slot-scanning standing, supine and fulcrum radiographs. Statistical analysis utilized ANOVA one-way tests and two-sample t tests to detail differences as indicated.

RESULTS

A total of 256 imaging studies were included, 75 slot-scanning standing, 112 supine, and 69 fulcrum radiographs. Fulcrum images only investigated thoracic curves and were, therefore, excluded from proximal thoracic and lumbar flexibility comparisons. Relevant mean standing curve magnitudes were similar between the groups with some variance in thoracic curves between fulcrum and supine image series (p = 0.003). There was no statistical difference in curve flexibility for proximal thoracic curves (p = 0.389) and lumbar curves (p = 0.798). However, for thoracic curves, slot-scanning standing images result in less measured curve flexibility compared to supine (p = 1.00E-7) and fulcrum images (p = 2.84E-18). Furthermore, supine bending images resulted in less measured curve flexibility in comparison to fulcrum images (p = 2.85E-7).

CONCLUSION

Slot-scanning standing bending films show comparable results in curve flexibility as supine bending films for proximal thoracic and lumbar curves but may show reduced flexibility for thoracic curves when compared to supine or fulcrum bending films. Given lower radiation dosing, slot-scanning films could be substituted for traditional supine films for assessment of proximal thoracic and lumbar curve flexibility.

Using Ultrasound to Screen for Scoliosis to Reduce Unnecessary Radiographic Radiation: A Prospective Diagnostic Accuracy Study on 442 Schoolchildren

Scoliosis screening is important for timely initiation of brace treatment to mitigate curve progression in skeletally immature children and adolescents. School scoliosis screening programs in Hong Kong follow the protocol of referring children screened positive with a scoliometer and Moiré topography for confirmatory standard radiography. Despite being highly sensitive (88%) in detecting those who require specialist referral, the screening program was found to have a false-positive rate >50%, which could lead to unnecessary X-ray radiation. Radiation-free ultrasound has been reported to be valid and reliable for quantitative assessment of curve severity in scoliosis patients. The aim of this prospective diagnostic accuracy study was to determine the accuracy of ultrasound in determining the threshold of referral that requires X-ray for children screened positive with the scoliometer and Moiré topography. Our study recruited 442 schoolchildren with a mean Cobb angle of 14.0 ± 6.6°. The sensitivity and specificity of ultrasound in predicting the correct referral status, confirmed by X-ray, were 92.3% and 51.6%, with positive and negative predictive values of 29.0% and 96.9%, respectively. Receiver operating characteristic curve analysis revealed area under the curve values of 0.735 for ultrasound alone and 0.832 for ultrasound in combination with measurement of angle of trunk rotation. The finding supports the accuracy of using ultrasound to determine referral status, which could result in a >50% reduction of unnecessary radiation for children undergoing scoliosis screening.

Equivalent Dose and Risk of Exposure Induced Cancer Death of Different Organs due to Various Image Techniques of EOS Imaging System

Background:

Euronext Paris Advanced Orthopedic Solutions (EOS) system is a new radiography system, capable of obtaining two-dimensional and three-dimensional images from bony structures in the body.

Objective:

The aim of this study is to estimate equivalent dose and the risk of exposure induced cancer death (REID) in different organs of body due to EOS imaging system.

Material and Methods:

In this experimental study, totally 120 patients were evaluated for various imaging techniques of lower limb, full spine and whole body. Equivalent dose and REID for colon, liver, lung, stomach, breast, bladder, ovary, blood cells (leukemia) and other organs were calculated using PCXMC software (version 2.0.1.2) based on Monte Carlo simulation of X-ray and human phantoms. The data on imaging technique, including age, sex, kVp, dose area product (DAP), mA, focal to detector distance were introduced as the input of PCXMC.

Results:

The maximum equivalent dose (mSv) due to EOS imaging system, was estimated for the bladder 0.240±0.066 for the full body technique and 0.240±0.093 for the lower limb technique, respectively, in both males and females. The maximum organ REID (incidence per million) due to EOS imaging system was estimated for lungs as 2.59±1.0 and 2.53±0.9, for the full body technique in both males and females, respectively.

Conclusion:

Generally, the equivalent dose and REID by EOS imaging system in different organs of body is low due to the low radiation dose received by the body in different techniques and views.

Image quality of EOS low-dose radiography in comparison with conventional radiography for assessment of ventriculoperitoneal shunt integrity

OBJECTIVE

Patients with shunted hydrocephalus often accumulate high levels of radiation over their lifetimes during evaluation of hardware integrity. Current practice involves the use of a series of conventional radiographs for this purpose. Newer low-dose EOS radiography is currently used to evaluate scoliosis but has not been explored to evaluate shunt integrity on a large scale. The goal of this study was to compare the quality of imaging using EOS low-dose radiography to conventional radiography to evaluate shunt tubing.

METHODS

A retrospective chart review was performed on 57 patients who previously had both conventional radiographs and low-dose EOS images of their cerebral shunt tubing from 2000 to 2018. Patient demographics (age, sex, type of shunt tubing, primary diagnosis) were collected. Conventional radiographic images and low-dose EOS images were independently analyzed by a neurosurgeon and neuroradiologist in three categories: image quality, delineation of shunt, and distinction of shunt compared to adjacent anatomy.

RESULTS

All patients had shunted hydrocephalus due to spina bifida and Chiari type II malformation. Ratings of EOS and conventional radiographic images by both raters did not differ significantly in terms of image quality (rater 1, p = 0.499; rater 2, p = 0.578) or delineation of shunt (p = 0.107 and p = 0.256). Conventional radiographic images received significantly higher ratings than EOS on the ability to distinguish the shunt versus adjacent anatomy by rater 1 (p = 0.039), but not by rater 2 (p = 0.149). The overall score of the three categories combined was not significantly different between EOS and conventional radiography (rater 1, p = 0.818; rater 2, p = 0.186). In terms of cost, an EOS image was less costly than a conventional radiography shunt series ($236-$366 and $1300-$1547, respectively). The radiation dose was also lower for EOS images, with an effective dose of 0.086-0.140 mSv compared to approximately 1.6 mSv for a similar field of view with conventional radiography.

CONCLUSIONS

The image quality of low-dose EOS radiography does not significantly differ from conventional radiography for the evaluation of cerebral shunts. In addition, EOS affords a much lower radiation dose and a lower cost.

Reducing the Breast Cancer Risk and Radiation Dose of Radiography for Scoliosis in Children: A Phantom Study

Full-spinal radiographs (FRs) are often the first choice of imaging modality in the investigation of scoliosis. However, FRs are strongly related to breast cancer occurrence due to multiple large-field radiographic examinations taken during childhood and adolescence, which may increase the risk for breast cancer in adulthood among women with scoliosis. The purpose of this study was to consider various technical parameters to reduce the patient radiation dose of FRs for scoliosis. To evaluate breast surface doses (BSDs) in FRs, radio photoluminescence dosimeters were placed in contact with a child phantom. Using the PC-based Monte Carlo (PMC) program for calculating patient doses in medical X-ray examinations, the breast organ dose (BOD) and the effective dose were calculated by performing Monte Carlo simulations using mathematical phantom models. The BSDs in the posteroanterior (PA) view were 0.15-0.34-fold those in the anteroposterior (AP) view. The effective dose in the PA view was 0.4-0.61-fold that in the AP view. BSD measurements were almost equivalent to the BODs obtained using PMC at all exposure settings. During FRs, the PA view without an anti-scatter grid significantly reduced the breast dose compared to the AP view with an anti-scatter grid.

The effect of added fat on the accuracy of Cobb angle measurements in CT SPR images: A phantom study

INTRODUCTION

Adolescent idiopathic scoliosis (AIS) is a spinal deformity that mostly affects females aged between 10 and 17 years old. Cobb's method is the gold standard for assessing AIS. Being overweight is a common characteristic in AIS patients; therefore, the aim of this study is to investigate the effect fat mass has on the accuracy of Cobb angle measurements in 10-year-old female AIS patients.

METHODS

A purpose-built phantom representing an AIS patient was scanned after adding several thicknesses of lard fat (0,2,4 and 8 cm). The phantom was scanned in an antero-posterior position using the scout mode of the CT scanner. 18 observers performed Cobb angle measurements on the images.

RESULTS

The average Cobb angle at 0 cm of fat was 10.83° (SD = 3.06), at 2 cm it was 10.90° (SD = 3.16), at 4 cm it was 10.64° (SD = 3.06) and at 8 cm it was 10.88° (SD = 3.02). No significant difference was observed between the measurements at these thicknesses.

CONCLUSION

Cobb angle measurements are not affected by the presence of fat.

IMPLICATIONS FOR PRACTICE

When assessing overweight AIS patients, it not necessary to manipulate the acquisition parameters, which could lead to increased patient dose, in order to get more accurate Cobb angle measurement.

The accuracy of Cobb angle measurement on CT scan projection radiograph images

INTRODUCTION

Adolescent idiopathic scoliosis (AIS) is a spinal deformity that can affect young children. It requires frequent exposure to X-rays to monitor the deformity, which can lead to the development of radiation-induced cancer later in life. The aim of this study is to test the accuracy of using scan projection radiography (SPR) in computed tomography (CT) scans for AIS assessment. This scanning mode delivers low radiation compared with conventional radiography.

METHOD

A bespoke phantom with a 14° scoliotic spine was scanned in CT SPR mode using 18 imaging acquisitions. These images were visually evaluated against set criteria to determine their suitability for Cobb angle measurements Those deemed of insufficient quality were excluded from the study (n = 8, excluded). Cobb angle measurements were then performed on the remaining images (n = 10, included) by 13 observers.

RESULTS

On average, the difference between the measured Cobb angle and the known angle was -2.75° (SD 1.46°). The agreement between the observers was good (p = 0.861, 95% CI 0.70-0.95) and comparable to similar studies on other imaging modalities which are used for Cobb angle estimation.

CONCLUSION

CT SPR images can be used for AIS assessment with the 5° margin of error that is clinically acceptable.

IMPLICATIONS FOR PRACTICE

The outcome is promising for patients and health providers because it provides an opportunity to reduce patient dose, achieve clinically acceptable Cobb angle measurements whilst using existing (CT) technology that is available in most hospital.